From: Jens Axboe <axboe@kernel.dk>
To: Anas Iqbal <mohd.abd.6602@gmail.com>,
Pavel Begunkov <asml.silence@gmail.com>
Cc: io-uring@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] io_uring: cast id to u64 before shifting in io_allocate_rbuf_ring()
Date: Mon, 16 Mar 2026 13:37:35 -0600 [thread overview]
Message-ID: <1f79957a-5b23-4bbd-af8d-9d1c86791645@kernel.dk> (raw)
In-Reply-To: <20260316150636.2123-1-mohd.abd.6602@gmail.com>
On 3/16/26 9:06 AM, Anas Iqbal wrote:
> Smatch warns:
> io_uring/zcrx.c:393 io_allocate_rbuf_ring() warn: should 'id << 16' be a 64 bit type?
>
> The expression 'id << IORING_OFF_PBUF_SHIFT' is evaluated using 32-bit
> arithmetic because id is a u32. This may overflow before being promoted
> to the 64-bit mmap_offset.
>
> Cast id to u64 before shifting to ensure the shift is performed in
> 64-bit arithmetic.
I'd be impressed if 'id' could be large enough to cause this to
overflow. AFAICT, you'd need more than 64K interface queues registered
to hit this. So I think this should be reframed as a cleanup, to appease
smatch.
I'll defer to Pavel on that one.
--
Jens Axboe
next prev parent reply other threads:[~2026-03-16 19:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-16 15:06 [PATCH] io_uring: cast id to u64 before shifting in io_allocate_rbuf_ring() Anas Iqbal
2026-03-16 19:37 ` Jens Axboe [this message]
2026-03-16 23:22 ` Pavel Begunkov
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